A San Francisco Police bomb squad vehicle drives through an area on Old Mason Street roped off by police after SFPD and Homeland Security officers arrested Ryan Chamberlain near the Beach Hut Cafe in Crissy Field on Monday, June 2, 2014 in San Francisco, Calif.

A San Francisco Police bomb squad vehicle drives through an area on...

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Special Agent in Charge David J. Johnson suggested the FBI intervened before the device could be used.

Photo: Tim Hussin, Special To The Chronicle

Special Agent in Charge David J. Johnson suggested the FBI...

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San Francisco police officers and an FBI agent direct a jogger away from the entrance to Crissy Field on Old Mason Street after SFPD and Homeland Security officers arrested Ryan Chamberlain near the Beach Hut Cafe on Monday, June 2, 2014 in San Francisco, Calif.

San Francisco police officers and an FBI agent direct a jogger away...

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A San Francisco police officer holds traffic to allow an SFPD bomb squad vehicle through onto Old Mason Street after SFPD and Homeland Security officers arrested Ryan Chamberlain near the Beach Hut Cafe in Crissy Field on Monday, June 2, 2014 in San Francisco, Calif.

Witness Morgan Manos, left, of San Francisco shows curious onlookers cellphone video he took of SFPD and Homeland Security officers arresting Ryan Chamberlain near the Beach Hut Cafe in Crissy Field on Monday, June 2, 2014 in San Francisco, Calif.

A bomb squad member investigates the automobile that Ryan Chamberlain was arrested in at Crissy Field in San Francisco on Monday, June 2, 2014.

Photo: Mathew Sumner, Special To The Chronicle

A bomb squad member investigates the automobile that Ryan...

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Federal agents were searching for Ryan Kelly Chamberlain II in connection with a raid in San Francisco on Saturday, May 31, 2014. An FBI official said Chamberlain is considered armed and dangerous, and driving a white Nissan Altima with California or Texas plates.

Photo: Courtesy, FBI

Federal agents were searching for Ryan Kelly Chamberlain II in...

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U.S. Park Police close off Old Mason St. to traffic at Crissy Field where Ryan Chamberlain was arrested on explosives charges in San Francisco on Monday, June 2, 2014.

Photo: Mathew Sumner, Special To The Chronicle

U.S. Park Police close off Old Mason St. to traffic at Crissy Field...

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Photo: Mathew Sumner

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U.S. Park Rangers turn pedestrians around at Crissy Field where Ryan Chamberlain was arrested on explosives charges in San Francisco on Monday, June 2, 2014.

Photo: Mathew Sumner, Special To The Chronicle

U.S. Park Rangers turn pedestrians around at Crissy Field where...

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Onlookers watch from a rooftop as FBI, HAZMAT, and SFPD personnel serve a warrant at a building on Jackson Street near Polk on May 31, 2014 in San Francisco, Calif.

Agents in haz-mat suits are seen as the FBI searches a building on Jackson St. between Polk and Van Ness in San Francisco, CA, Saturday May 31, 2014.

Photo: Michael Short, The Chronicle

Agents in haz-mat suits are seen as the FBI searches a building on...

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A neighbor looks out of his window as the FBI searches a building on Jackson St. between Polk and Van Ness in San Francisco, CA, Saturday May 31, 2014.

Photo: Michael Short, The Chronicle

A neighbor looks out of his window as the FBI searches a building...

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Agents in haz-mat suits are seen as the FBI searches a building on Jackson St. between Polk and Van Ness in San Francisco, CA, Saturday May 31, 2014.

Photo: Michael Short, The Chronicle

Agents in haz-mat suits are seen as the FBI searches a building on...

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Agents in haz-mat suits are seen as the FBI searches a building on Jackson St. between Polk and Van Ness in San Francisco, CA, Saturday May 31, 2014.

Photo: Michael Short, The Chronicle

Agents in haz-mat suits are seen as the FBI searches a building on...

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Agents in haz-mat suits are seen as the FBI searches a building on Jackson St. between Polk and Van Ness in San Francisco, CA, Saturday May 31, 2014.

Photo: Michael Short, The Chronicle

Agents in haz-mat suits are seen as the FBI searches a building on...

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FBI spokesperson Peter Lee addresses the press on Turk St. regarding Saturday's investigation of an apartment on Polk St. in San Francisco, Calif. on Sunday, June 1, 2014. FBI and SFPD investigated the apartment of Ryan Kelly Chamberlain II for dangerous materials.

Photo: James Tensuan, The Chronicle

FBI spokesperson Peter Lee addresses the press on Turk St....

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FBI spokesperson Peter Lee addresses the press on Turk St. regarding Saturday's investigation of an apartment on Polk St. in San Francisco, Calif. on Sunday, June 1, 2014. FBI and SFPD investigated the apartment of Ryan Kelly Chamberlain II for dangerous materials.

Photo: James Tensuan, The Chronicle

FBI spokesperson Peter Lee addresses the press on Turk St....

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Agents in haz-mat suits are seen as the FBI searches a building on Jackson St. between Polk and Van Ness in San Francisco, CA, Saturday May 31, 2014.

Photo: Michael Short, The Chronicle

Agents in haz-mat suits are seen as the FBI searches a building on...

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A law enforcement agent hangs a curtain to obstruct the view of the public and the press while FBI agents serve a warrant at a building on Jackson Street near Polk on May 31, 2014 in San Francisco, Calif.

A person wearing a HAZMAT suit gestures after leaving a building on...

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Law enforcement agents in HAZMAT suits help decontaminate and remove the suit of an agent that just exited a building on Jackson Street near Polk where the FBI was serving a warrant on May 31, 2014 in San Francisco, Calif.

The San Francisco political and media consultant who was arrested after a three-day manhunt had a model rocket motor, a circuit board, ball bearings, screws and other items in his apartment - materials for a remote-controlled bomb that was "designed to maim or kill," the FBI said Tuesday.

Agency officials, though, did not say whether they had any information indicating that Ryan Chamberlain planned to use the equipment discovered in a Saturday raid. They suggested they had sought to intervene before he had a chance.

The description of the materials was another puzzling development in the investigation of Chamberlain, who is well-known in Bay Area political circles and who, during his time as a fugitive, posted a "Goodbye" letter to Facebook saying he was depressed and had "scoured the Internet absorbing fuel for morbid fantasies."

The alleged bomb-making supplies were in a rust-colored messenger bag found on the dining room floor of Chamberlain's apartment on Polk Street, FBI Special Agent Michael Eldridge said in a court affidavit unsealed Tuesday.

The bag also allegedly held batteries, a green powder and an electric igniter. In sum, Eldridge wrote, the bag contained the four components of an improvised bomb: a power source, wire conductors, a switching mechanism and an explosive.

"FBI bomb technicians believe that the circuit board ... was designed to serve as a remote control, allowing detonation of the device from afar," the affidavit stated.

Suicide note posted

Chamberlain was arrested Monday evening, hours after he posted what appeared to be an online suicide letter to his 718 Facebook friends. On Tuesday, he was formally charged with acquiring bomb-making materials, as some of his friends rallied to support him.

Chamberlain, 42, made a brief appearance at the U.S. District Court in San Francisco, where he was charged with a count of possessing an illegal destructive device that carries a maximum punishment of 10 years in prison and a $10,000 fine.

Appearing calm and collected, and in the same sweatshirt and shorts he had worn when he was arrested the night before, Chamberlain spoke only in response to the judge, saying, "Yes, your honor." He did not enter a plea, and was ordered to return Wednesday and Thursday for further hearings.

At a news conference, David J. Johnson, the special agent in charge of the FBI's San Francisco division, said the public faced no safety threat after the arrest. But he gave few details about why agents investigated Chamberlain and what they believe he planned to do with the bomb materials.

Suspect questioned

The unsealed affidavit revealed that the FBI had obtained the warrant to search Chamberlain's apartment - where he allegedly lived alone - on Friday. The next morning, Eldridge said, law enforcement officers spotted Chamberlain leaving his unit with a woman, but did not arrest him, apparently because the alleged bomb materials had not yet been discovered.

Eldridge said that when Chamberlain returned 30 minutes later, he invited Chamberlain to talk in a nearby coffee shop. There, Chamberlain "admitted that he was aware of the Tor network, and that he sometimes played poker on 'black market' websites," according to the affidavit.

The Tor network conceals online communications. Eldridge did not detail why the FBI was interested in the activity.

'Reckless' driving

After a short interview, Eldridge said, Chamberlain asked to leave and was allowed to do so. Surveillance teams tried to follow him in his car but cut off the pursuit "out of a concern for public safety," after Chamberlain drove in a "reckless manner at a high rate of speed, failing to stop at posted lights and signs."

After that, the search was conducted, and the bomb materials were found, Eldridge wrote.

Chamberlain's whereabouts were unknown until Monday afternoon, when the FBI learned his ATM card had been used in a bar on Haight Street. He was then taken into custody about 6:30 p.m. near Crissy Field after a bystander and then two city police officers recognized him, officials said.

San Francisco Police Chief Greg Suhr described the arrest at Tuesday's news conference and called Chamberlain a "very dangerous and desperate person," citing the letter posted to Facebook. He asked other members of the public to alert authorities if they believe someone in their life appears to be in a similar crisis.

Longtime struggles

Chamberlain's letter posted to Facebook described longtime struggles with depression along with a romantic heartbreak and the recent loss of a job. In a follow-up post to Facebook and Twitter, he said he had "explored some ugly websites a year-ish ago," but he added, "No one was ever in danger. And recently I was all better."

Chamberlain said he had used a program, HootSuite, to delay the posting of the letter. As they read it, many of his friends feared he was already dead.

Chamberlain, who uses the online handle Poliholic, moved to the city from Iowa at age 30. He worked for consulting firms on elections and once ran for a seat on the Republican Party County Central Committee in San Francisco, the party's local organizing body.

More recently, he did public relations work for technology, apparel and marketing firms. In 2012, he worked as an independent contractor for The Chronicle and promoted the San Francisco 49ers Insider iPad app on social media.

Friends fund defense

The FBI's nationwide manhunt for Chamberlain and the media coverage of the pursuit had prompted criticism from some of his friends and supporters.

Adriel Hampton, 35, a former San Francisco political reporter who now lives in Los Angeles, started a crowdfunded legal defense account for Chamberlain on Monday.

"The complaint is very serious," he said Tuesday after learning of the FBI affidavit. "It doesn't change the fact that a lot of people care about him, and we're glad nothing happened."

Hampton said he was "proud to be one of the dozens of people who will stand up for Ryan. I want people to known that this guy has a community. He's not just a crazy terrorist. He's obviously going through a crisis. I'm glad he was arrested, and he's not dead. I thought he had killed himself."